The increasing demands being made that diesel engines be operationally safe, economical and compatible with the environment are necessitating use of injection systems which are increasingly costly. It has been shown that only minimal advantages can be gained with respect to the before-mentioned requirements when using diesel engines with conventional injection systems. Research which has been carried out in the last several years has, therefore, been aimed at developing a high pressure injection system having marked improvement in the operating characteristics of a diesel engine. In particular, additional and more significant improvements with respect to the before-mentioned requirements are to be expected whenever the initiation of injection, the amount of fuel injected and pilot injection can be optimized for each operating level of the diesel engine.
It is known that a preliminary or pilot injection can be produced by interrupting the injection process by short-term emptying of the high pressure pump chamber of the injection pump. During this interruption, the fuel pressurized by movement of the pump piston of the injection pump is routed to an equalizing chamber in which there is an equalization piston which is biased by means of pressure which can be varied depending on speed. This prior system does not provide for a complete separation of fuel and the hydraulic fluid of the additional pressure system.